Venous plexus-associated lymphoid hubs support meningeal humoral immunity

There is increasing interest in how immune cells in the meninges, the membranes that surround the brain and spinal cord, contribute to homeostasis and disease in the central nervous system (CNS)1,2. The outer layer of meninges, the dura mater, has recently been described to contain both innate and adaptive immune cells, and function as a site for B cell development. Here, we identified organised lymphoid structures protecting fenestrated vasculature in the dura mater that we term dural-associated lymphoid tissue (DALT). We found the most elaborate immune organization, including lymphatic vessels, surrounding the rostral_x0002_rhinal confluence of sinuses. We termed this structure that interfaced with the skull bone marrow and a comparable venous plexus at the skull base, the rostral-rhinal venolymphatic hub. Immune aggregates were present in DALT during homeostasis and expanded with age or following challenge with systemic or nasal antigens. DALT contained germinal centre (GC) B cells, and supported the generation of somatically mutated, antibody-producing cells in response to a nasal pathogen challenge. Inhibition of lymphocyte entry into the rostral-rhinal hub at the time of nasal viral challenge abrogated the generation of germinal centre B cells and class-switched plasma cells, as did perturbation of B-T cell interactions. These data demonstrate lymphoid architecture around vasculature in dura mater that can sample antigens and rapidly support humoral immune responses following local pathogen challenge. Overall design: Rostral rhinal hubs isolated from the dorsal meninges were analyzed by scRNAseq in two groups of mice (uninfected vs day 8 post-VSV infection) in two independent experiments. Experiment#1: uninfected (Men_Naive), d8 VSV (Men_VSV); Experiment#2: uninfected (PBS_HUB), d8 VSV (VSV_HUB)

近年来，学界对脑膜——即包裹脑与脊髓的被膜——中的免疫细胞如何参与中枢神经系统（Central Nervous System，CNS）的稳态维持与疾病进程的研究关注度与日俱增。作为脑膜最外层的硬脑膜（dura mater），近期研究证实其不仅含有先天免疫与适应性免疫细胞，还可作为B细胞发育的重要位点。本研究中，我们鉴定出硬脑膜中包裹有孔脉管系统的有序淋巴样结构，并将其命名为硬脑膜相关淋巴组织（dural-associated lymphoid tissue，DALT）。我们观察到，在吻侧-嗅区静脉窦汇合处周围存在最为复杂的免疫组织结构，其中包含淋巴管。我们将这一与颅骨骨髓及颅底同类静脉丛相连的结构命名为吻侧-嗅区静脉淋巴枢纽（rostral-rhinal venolymphatic hub）。稳态条件下，DALT中即存在免疫聚集物；该聚集物可随年龄增长，或在接受全身性、鼻腔抗原刺激后发生扩增。DALT中包含生发中心（germinal centre，GC）B细胞，且可在鼻腔病原体刺激下，介导体细胞突变型抗体产生细胞的生成。在鼻腔病毒刺激时阻断淋巴细胞进入吻侧-嗅区枢纽，或扰乱B细胞与T细胞的相互作用，均可消除生发中心B细胞与类别转换浆细胞的生成。上述研究结果证实，硬脑膜脉管周围存在淋巴样结构，该结构可捕获抗原，并在局部病原体刺激后快速介导体液免疫应答。
实验整体设计：本研究通过两项独立实验，对两组小鼠（未感染组与水疱性口炎病毒（vesicular stomatitis virus，VSV）感染后第8天组）背侧脑膜分离得到的吻侧-嗅区枢纽进行了单细胞RNA测序（single-cell RNA sequencing，scRNAseq）分析。实验1：未感染组（Men_Naive）、VSV感染第8天组（Men_VSV）；实验2：未感染组（PBS_HUB）、VSV感染第8天组（VSV_HUB）